HONG KONG (Reuters) - The authorities have busted a prostitution syndicate in Macau, the world's biggest gambling hub, and arrested six people, including a nephew of gaming magnate Stanley Ho, the media reported on Tuesday.

Those arrested came from Hong Kong, Macau and the Chinese mainland. Ninety-six women from the mainland and Vietnam were also detained, the Macau police said in a Jan 10 statement, but did not identify those arrested.

Mr Alan Ho, who is a senior executive at Hotel Lisboa and a nephew of SJM Holdings' chairman Stanley Ho, and five hotel staff were among those arrested, the South China Morning Post newspaper said.

SJM officials were not immediately available to comment. A spokesman for Hotel Lisboa declined to comment, and a spokesman for the Macau Judiciary Police declined to identify those arrested.

The authorities said the syndicate had run for more than a year, generating a profit of 400 million patacas (S$66.8 million). Each woman had to pay a membership fee of 150,000 patacas and a monthly "protection fee" of 10,000 patacas.

Gambling revenue in Macau, the only place in China where casino gambling is legal, fell 2.6 percent to 351.5 billion patacas in 2014, its first annual decline since casinos were liberalised in 2001.

Last month, Chinese President Xi Jinping urged Macau to hasten diversification away from its bread-and-butter casino industry, which has lost about US$60 billion (S$80 billion) in market value over the last six months.